It has already been proposed to use a carbodiimide compound as an end-sealing agent for a polymer having a terminal acid group such as a carboxyl group so as to suppress the hydrolysis of the polymer (Patent Documents 1 and 2). The carbodiimide compound used in this proposal is a linear carbodiimide compound.
When the linear carbodiimide compound is used as an end-sealing agent for polymers, a compound having an isocyanate group is liberated by a reaction for bonding the linear carbodiimide compound to an end of the polymer to produce a smell peculiar to an isocyanate compound, thereby deteriorating the work environment.
Patent Document 3 discloses a macrocyclic carbodiimide compound. Since this compound is produced as a highly diluted solution, the concentration of the macrocyclic carbodiimide compound is low, whereby it takes many days to react it with a polymer and therefore the utility of the macrocyclic carbodiimide compound as an end-sealing agent for polymers is low. Since the molecular weight of the macrocyclic carbodiimide compound is high with respect to the carbodiimide group, the efficiency of the macrocyclic carbodiimide compound as an end-sealing agent for polymers is low. Further, Patent Document 3 does not take into consideration the reduction of an isocyanate smell produced by the end-sealing of a polymer. This macrocyclic carbodiimide compound has a long chain, is readily decomposed at a high temperature and therefore is not suitable for use as an end-sealing agent for polymers having a high melting point such as polyesters.    (Patent Document 1) JP-A 2008-050584    (Patent Document 2) JP-A 2005-2174    (Patent Document 3) US-A 2008/0161554